What type of stress occurs when forces are applied in opposite directions along a single line?

The type of stress that occurs when forces are applied in opposite directions along a single line is shear stress. Shear stress arises when an external force causes different sections of a material to slide past one another, typically along a plane parallel to the direction of the applied forces.

In a shear situation, think of a pair of scissors cutting through paper; the blades apply opposing forces at a very small area, which causes the material to shear. This is distinctly different from other forms of stress mentioned.

Compression occurs when forces push towards each other, causing material to shorten, while bending involves a combination of tensile and compressive stresses across a beam or similar structure. Torsion, on the other hand, refers to twisting forces applied in a helical manner, causing shear stress but in a specific twisting motion rather than along a straight line. Understanding the characteristics of shear stress is crucial in aircraft metal structural repair, as many joints and connections experience shear forces during operation.